1. Field of the Invention
The present invention relates to a control apparatus that performs focus control based on a signal output from an image pickup element.
2. Description of the Related Art
Previously, focus detection (phase difference AF) by an imaging-plane phase-difference detection method using focus detection signals from an image pickup element and focus detection (contrast AF) by a contrast method using imaging signals from the image pickup element have been known.
Japanese Patent Laid-open No. 2013-25246 discloses an image pickup apparatus which performs focus control by using a phase difference AF by a correlation calculation unit and a contrast AF by a contrast evaluation unit. The image pickup apparatus disclosed in Japanese Patent Laid-open No. 2013-25246 first performs the phase difference AF based on a correlation value by the correlation calculation unit up to a neighborhood of an in-focus position. After performing the phase difference AF, the image pickup apparatus performs the contrast AF by the contrast evaluation unit when a contrast evaluation value obtained by a shift addition image becomes available.
The correlation calculation unit as disclosed in Japanese Patent Laid-open No. 2013-25246 needs to correspond to a larger amount of defocus (shift amount from an in-focus position), and therefore a filtering process is performed to detect a signal with a lower spatial frequency band relative to the contrast evaluation unit in many cases. Accordingly, in-focus determination positions obtained by both of the contrast evaluation unit and the correlation calculation unit have a displacement (shift amount) due to the difference of the bands of filters.
Therefore, in the configuration disclosed in Japanese Patent Laid-open No. 2013-25246, when an instruction of start of AF is given again after the AF control to the in-focus position or the completion of shooting an image, the focus detection by the phase difference AF is performed by using the correlation calculation unit again even when the change of the defocus state of an object is small. In this case, the in-focus position may be misidentified by the displacement due to the difference of the bands of the filters as described above and thus a focus lens may be unnecessarily driven, and as a result, there is a possibility that high-speed and high-accuracy focus detection is prevented.